The present invention relates to optical switches. More particularly, the present invention relates to getters for removing atmospheric gases from optical switches.
One type of optical switch is based on inkjet printer technology and planar lightwave circuit technology. These optical switches route an optical stream from one path to another without having to convert the signal from optical, to electronic, and back to optical. Instead, these optical switches use bubbles, which are formed by vaporizing the fluid in the optical switch, to switch light signals from one optical fiber to another. The optical switches have a planar lightwave circuit, which includes a grid of intersecting paths or waveguides, mounted on a matrix controller substrate. At a cross point of two waveguides is a trench filled with fluid that has the same optical properties as the glass in the waveguides. As a result, light or an optical stream and its communications contents can travel unimpeded through the cross point.
When the optical signal needs to be rerouted, a bubble heater warms the appropriate trench to insert a vapor bubble at the cross point. The vapor bubble alters the optical properties of the cross point, thereby causing the light to be reflected along a different path. The bubbles can be formed and removed hundreds of times per second, providing a fast and reliable switching function, one without the use of mirrors or other mechanical moving parts.
One problem with this type of optical switch, however, is that atmospheric gases, such as oxygen, nitrogen, carbon dioxide, and water vapor, can seep into the optical switch and accumulate in the fluid. Because this optical switch uses vapor bubbles rather than air bubbles, a substantial accumulation of atmospheric gases can affect the performance of the optical switch. At present, these optical switches lack any sort of mechanism for removing unwanted atmospheric gases from the fluid.
Common metallic getter materials, such as zirconium-titanium alloys, have been used to purify inert gases. In inert gas purification applications, these metallic getters are typically heated to temperatures above 300xc2x0 C. to improve their efficiency. The optical switches, however, operate a temperatures much lower than 300xc2x0 C. and are adversely affected by the higher temperatures needed to activate metallic getters. Temperatures above 300xc2x0 C. can damage the solder seals of the optical switch and cause the working fluid to degrade and react with the getter. In addition, metallic getters may not activate if they are in contact with a fluid, such as the working fluid of the optical switch. It would be desirable, however, to incorporate metallic getters into these optical switches, since at lower temperatures (e.g., less than 100xc2x0 C.) metallic getters absorb or react with atmospheric gases, but not with more complex, inert compounds.
There is a need, therefore, for a getter that can be incorporated into an optical switch to remove accumulated atmospheric gases from the fluid in the optical switch over its operational life. In addition, it would be desirable for a getter to purify the fluid in a fill station prior to insertion of the fluid into the optical switch.
In accordance with one embodiment of the present invention, an optical switch includes a core and a fluid reservoir connected to the core. The core includes a base, a matrix controller substrate mounted on the base, and a planar lightwave circuit mounted on the matrix controller substrate. The planar lightwave circuit has a plurality of waveguides and a plurality of trenches. Each trench is located at a cross point or intersection of two waveguides. The fluid reservoir, which is coupled to the core via a tube, contains a fluid, which the fluid reservoir supplies to the plurality of trenches of the core. The optical switch further includes a getter for removing accumulated atmospheric gases from the fluid. The getter may be a porous silica getter, a non-evaporable getter, or an evaporable getter. The optical switch may further include a membrane that separates a getter chamber from a fluid chamber. The getter chamber and the fluid chamber may be located in the fluid reservoir. Alternatively, the getter chamber and the fluid chamber are separate containers that are coupled together by a connecting tube, with the membrane disposed in the connecting tube. The membrane may be a molecular sieve or a polymeric compound that allows atmospheric gases but not fluid, in either liquid or vapor form, to pass from the fluid chamber to the getter chamber.
In accordance with another embodiment of the present invention, a method of making an optical switch includes providing an optical switch having a core and a fluid reservoir coupled to the core via a tube and inserting a getter into the fluid reservoir. The optical switch has the features described above. The method further includes activating the getter in the fluid reservoir by connecting the fluid reservoir to a vacuum and heating the getter. The fluid reservoir is then filled with fluid from a fill station, and the fluid reservoir is sealed. The fluid reservoir may be divided by a membrane into a getter chamber, in which the getter is inserted, and a fluid chamber, which is filled with fluid from the fill station.
In accordance with still another embodiment of the present invention, a method of making an optical switch includes providing an optical switch having a core and a fluid reservoir coupled to the core via a supply tube, connecting the fluid reservoir of the optical switch via a supply tube to a fill station containing fluid, and inserting a getter into the fill station. The getter is activated in the fill station under a vacuum to purify the fluid in the fill station. The fluid is then supplied through the supply tube and into the fluid reservoir. The method further includes inserting a second getter into the fluid reservoir of the optical switch and activating the second getter prior to filling the reservoir with fluid from the fill station. The fluid reservoir may be divided, by a membrane that allows gas but not fluid to pass through, into a getter chamber containing the second getter and a fluid chamber.